Sympathetic cooling of molecules with laser-cooled atoms

Alisdair O. G. Wallis, Edward J. J. Longdon, Piotr Szymon Żuchowski +1 more

Eunmi Chae

Takashi Baba, Izumi Waki

This paper presents the first sympathetic cooling of molecular ions using laser-cooled atomic ions. To this end, we developed a novel combination of sympathetic cooling and in situ mass spectroscopy that allows the use of laser-cooled atomic ions to detect sympathetically-cooled molecular ions non-destructively. We demonstrate this technique by cooling and mass-analysing ions of ultra-high-vacuum residual gas and externally introduced air in situ with less than 80 ions each, confined in a radio-frequency quadrupole (RFQ). This capability to detect and identify sympathetically-cooled molecules with potentially-high sensitivity in situ in an RFQ should be useful for molecular spectroscopy, chemical analysis and study of cold molecules and clusters.

P. Pillet, Matthieu Viteau, Amodsen Chotia +5 more

Jeff. Berglund, Michael Drewsen, Christiane P. Koch

Sympathetic cooling of molecular ions through the Coulomb interaction with laser-cooled atomic ions is an efficient tool to prepare translationally cold molecules without, ideally, affecting the internal state of the molecular ions. However, the electric field due to the Coulomb interaction may induce rotational transitions that change the purity of initially quantum state prepared molecules. Here, we use estimates of rotational state changes in single collisions of diatomic ions with atomic ions [J. M. Berglund, M. Drewsen, and C. P. Koch, ] to determine the overall rotational excitation accumulated over the sympathetic cooling. Considering two different experimental scenarios, that of a molecular ion cotrapped with a single atomic ion and a molecular ion immersed in a Coulomb crystal of atomic ions, we also estimate the cooling time.

Noah J. Fitch, Michael R. Tarbutt